Characterization of chloramphenicol acetyltransferase from chloramphenicol-resistant Staphylococcus aureus.

Chloramphenicol-resistant strains of Staphylococcus aureus contain an inducible enzyme which inactivates chloramphenicol by acetylation in the presence of acetyl coenzyme A. The products of acetylation are chromatographically indistinguishable from those obtained with chloramphenicol-resistant Escherichia coli harboring an R factor. The kinetics of induction of chloramphenicol acetyltransferase are complicated by the inducer's effect on protein biosynthesis and its fate as chloramphenicol 3-acetate, which is not an inducer of the enzyme. The E. coli and S. aureus enzymes have been compared, with the conclusion that they are identical with respect to molecular weight (approximately 78,000) and pH optimum (7.8), but differ with respect to heat stability, substrate affinity, electrophoretic mobility, and immunological reactivity. Antiserum prepared against enzyme from E. coli contains precipitating antibody, which inactivates the E. coli enzyme, but neither precipitates nor neutralizes the activity of S. aureus enzyme.